Features of the nervous system of flatworms. Flatworms, structural features, excretory system. Organ system name
Initial level of knowledge:
Response Plan:
- External and internal structure of flatworms
- Reproduction of Flatworms
- Classification of Flatworms, variety of species
- Peculiarities of the structure and development of worms of the Ciliate class using the example of the Milk planaria
- Features of the structure and development of worms of the class Flukes using the example of the Liver fluke
- Features of the structure and development of worms of the Tapeworm class using the example of the Bull tapeworm and others.
General characteristics of flatworms
This is released from the planarian by diffusion. To perform aerobic respiration, the planarian must get oxygen into the cells of its body. Oxygen enters the planarian by diffusion. These structures can be considered primitive buds. They are unique to the phylum. Fangs are mainly parasites of vertebrate animals. The animals usually have a sucker around the mouth and one on the ventral surface. These suckers allow the animal to cling to the body organs in which they live. Many flies have immature stages that live in other animals.
For example, immature stages of the human jaw live in snails. They are released from snails, and the second immature stage lives in fish. When people ingest raw or undercooked fish, they are also ingesting immature stages of chance. The immature stages migrate to the bile ducts of the liver, where they mature. Although there they cause liver damage and can lead to human death. The eggs are produced by adults in the bile ducts. The eggs pass through the bile ducts into the digestive tract and exit the host in the feces.
Number of types: about 25 thousand.
Habitat: They live everywhere in humid environments, including the tissues and organs of other animals.
Structure: Flatworms- these are the first multicellular animals in which, in the course of evolution, bilateral symmetry, three-layer structure, real organs and tissues appeared.
Bilateral(bilateral) symmetry - this means that an imaginary axis of symmetry can be drawn through the animal’s body, with the right side of the body being a mirror image of the left.
The eggs are swallowed by the snails and the cycle repeats. People can also become infected by human chance. The immature stages of this accident also live inside the snails. These larvae leave the snail and are present on the ground in areas of poor sanitation. Immature stages enter humans by burrowing through the skin of the human host. Immature flies enter the blood vessels and mature there.
They can cause anemia and damage to the liver, bladder and brain. Tapeworms are also parasitic flatworms. People can become infected with tapeworms by eating raw or undercooked pork or beef. Ingest tapeworm larval stages present in the muscles of pigs or cows. The tapeworm attaches to the intestines by moving through the digestive tract using hooks or suckers. The moonworm matures and grows in the intestines, a nutrient medium.
During embryonic development in three-layer animals have three layers of cells: outer - ectoderm, average - mesoderm, internal – endoderm. From each layer certain organs and tissues develop:
the skin (epithelium) and the nervous system are formed from the ectoderm;
from the mesoderm - muscle and connective tissue, reproductive and excretory systems;
The moonworm grows longer after sensing. The buds are called "proglottids". Each proglottid contains reproductive structures and eggs, which are produced and fertilized in each segment. The oldest proglottids break off the tapeworm and leave the host with the feces. In areas of poor sanitation, pigs or cows consume the zygotes. The immature stages burrow into the muscle tissue of the pig or cow and the cycle repeats.
The phylum also includes plant parasites that infect plant roots. These parasitic nematodes reduce the productivity of many human crops. The phylum includes several human parasites. First, roundworms have a complete digestive system. This means that there are two openings for the digestive system. The mouth at the front swallows or swallows food, while the anus at the back secretes digestive waste. A complete digestive system is much more effective than intestinal meal.
from the endoderm - the digestive system.
In flatworms, the body is flattened in the dorso-abdominal direction, there is no body cavity, the space between the internal organs is filled with mesoderm cells (parenchyma).
Digestive system includes the mouth, pharynx and blind intestine. Absorption of food and excretion of undigested residues occurs through the mouth. Tapeworms have a completely absent digestive system; they absorb nutrients over the entire surface of the body, being in the intestines of the host.
A complete digestive system allows for continuous processing of food. The roundworm can feed continuously, food digestion can occur continuously, and waste can be continuously excreted. Animals with puffin gut must wait for their food to be digested, expel digestive waste from their mouths, and then swallow their next meal. The presence of this structure allows space and cushioning for organs, provides the roundworm with a hydraulic skeleton, and helps distribute food from the digestive tract to other cells of the worm.
excretory organs – protonephridia. They consist of thin branching tubules, at one end of which there are flame (flickering) cells star-shaped, immersed in the parenchyma. A bunch of cilia (flickering flame) extends inside these cells, the movement of which resembles the flickering of a flame (hence the name of the cells). Flame cells capture liquid decay products from the parenchyma, and cilia drive them into the tubule. The tubules open on the surface of the body as an excretory pore, through which waste products are removed from the body.
Several human parasites are roundworms. Many people in tropical countries are infected with nematodes. Immature stages of this parasitic worm burrow through the skin, pass through the blood vessels into the lungs, enter the air spaces of the lungs and crawl into the esophagus. The immature stage is then swallowed. The worm attaches to the intestine with hooks and matures into adulthood. Fertilized eggs are released in the feces and zygotes develop into immature stages on the soil. When people walk barefoot on soil, they become infected.
A mature scoundrel drinks blood and lymph juices. They cause anemia due to blood loss. Human roundworm is common when human feces are used as plant fertilizer. Humans ingest eggs when they eat plant material. Immature stages pass through the human body in the blood vessels. Mature human roundworms live in the intestines, where they produce eggs that are released in the feces.
Nervous system ladder type ( orthogon). It is formed by a large head paired nerve ganglion (ganglion) and six nerve trunks extending from it: two on the ventral side, two on the dorsal and two on the sides. The nerve trunks are connected to each other by jumpers. Nerves extend from the ganglion and trunks to organs and skin.
Reproduction and development:
People can accidentally become infected with trichina worm by eating unpaved port. Pork muscle may contain immature stages of the trichinal worm. When people ingest the larval stage, it matures in the intestines where adult worms reproduce. Immature stages migrate from the intestine into muscle tissue. Because people don't usually eat, the cysts become coated with calcium carbonate. We call this condition trichinosis.
What are the types of digestion and digestive system of Platygminths?
Most well-known representatives Platyhelminths are worms that cause human diseases such as tania and schistosome. Planaria, as it has been widely studied in biology, is also well known. This is the main external morphological feature that distinguishes them from nematodes. How many germ layers make up the body of lamellar mines? How are they classified according to this feature. Flatworms have incomplete digestive systems and use extracellular and intracellular complementary digestion.
Flatworms are hermaphrodites. Sex cells mature in the sex glands (gonads). A hermaphrodite has both male glands - testes, and female glands - ovaries. Fertilization is internal, usually cross-fertilization, i.e. worms exchange seminal fluid.
CLASS cilia worms
Milk planaria, a small aquatic animal, the adult is ~25 mm long and ~6 mm wide, with a flat, milky white body. At the front end of the body there are two eyes that distinguish light from darkness, as well as a pair of tentacles (chemical sense organs) necessary for searching for food. Planarians move, on the one hand, thanks to the work of the cilia covering their skin, and on the other hand, thanks to the contraction of the muscles of the skin-muscular sac. The space between the muscles and internal organs is filled with parenchyma, in which they meet intermediate cells, responsible for regeneration and asexual reproduction.
How are nutrients distributed throughout the digestive system in planaria?
How gas exchange occurs in flatworms
Plasticine digestive system. . Platyhelminths exchange gases exclusively by diffusion through their body surface. This is only possible because all the cells are located relatively close to each other as gases diffuse throughout the cell.Porifera and cnidarians do not have excretory systems. Are there lamellar larvae in the leaching system? What is an example of freshwater flatworm? What physiological problem must these animals solve while living in this environment? Freshwater tileminths such as planaria have an internal environment that is more concentrated in solutes than their external environment and, as a result, tend to obtain water. These organisms require a drainage system to avoid cell death caused by excess water.
Planarians are predators that feed on small animals. The mouth is located on the ventral side, closer to the middle of the body, from it comes a muscular pharynx, from which three branches of a closed intestine extend. Having captured the victim, the planaria sucks out its contents with its throat. Digestion occurs in the intestines under the action of enzymes (intestinal), and intestinal cells are able to capture and digest pieces of food (intracellular digestion). Undigested food remains are removed through the mouth.
This problem is solved by the presence of protonephridia located along the longitudinal canals in their body. Protonephridia have ciliated cells called flame cells that expel water outside the body through excretory pores. Is the Platygminth nervous system more or less complex than the nervous system? What are the main neural structures found in flatworms? How this neural organization is important for the diversity of ecological niches explored by species of the phylum. In Platyhelminths one can see the beginning of the cephalization process with a concentration of neurons in the anterior part of the body and the appearance of photoreceptor cells in the ocelli.
Reproduction and development. Ciliated animals are hermaphrodites. Cross fertilization. Fertilized eggs fall into a cocoon, which the worm lays on underwater objects. Development is direct.
CLASS FLUKES
CLASS TAPPEWORMS
Bull tapeworm– a tapeworm, reaches a length of 4 to 12 meters. The body includes a head with suckers, a neck and a strobila - a band of segments. The youngest segments are located at the neck, the oldest are sacs filled with eggs, located at the posterior end, where they come off one by one.
Due to the increased ability of these animals to perceive and interact with their environment, thanks to the increased complexity of their neural network, platyhelminths can be found in a variety of environments and life patterns, including terrestrial ones, and with a variety of lifestyles, including parasitic and free-living species.
How does lateral symmetry contribute to cephalization?
Cephalization is the evolutionary tendency to concentrate neural control in central structures in which neurons are grouped. Through lateral symmetry, the body can be divided into lateral parts: upper, lower, anterior and posterior. These parts must be integrated and controlled in some way, and this need gave rise to ganglionic complexity and organisms with a head, the privileged extremity of the bilateral body where the nervous central command and important sensory organs are located.
Reproduction and development. The bovine tapeworm is a hermaphrodite: each of its segments has one ovary and many testes. Both cross-fertilization and self-fertilization are observed. The posterior segments, filled with mature eggs, open and are excreted with feces. Cattle (intermediate host) can swallow eggs along with grass; in the stomach, microscopic larvae with six hooks emerge from the eggs, which enter the blood through the intestinal wall and are carried throughout the animal’s body and carried into the muscles. Here the six-hooked larva grows and turns into Finn- a bubble containing the head of the tapeworm with its neck. A person can become infected with finches by eating undercooked or undercooked meat from an infected animal. In the human stomach, a head emerges from the finca and attaches to the intestinal wall. New segments bud from the neck - the worm grows. Bovine tapeworm secretes toxic substances that cause intestinal disorders and anemia in humans.
How can we describe asexual reproduction in a planarian?
Review of Flatworms - Variety of Images: Cephalization. . Planaria can divide asexually by transverse bipartition due to the great ability to regenerate their tissues. When they attach to a substrate, they can cause a constriction in their midsection, dividing their body into two parts, each producing a new pattern as the tissue regenerates.
Is it possible for hermaphrodite species to cross-fertilize?
Hermaphroditic species of animals and plants carry out cross-fertilization mainly due to the maturation of female and male structures in different periods. Cross-fertilization occurs in planarians, which are hermaphrodites in which sexual fertilization occurs with male and female gametes from different specimens. These specimens combine their sexual structures and exchange gametes.
Development pork tapeworm has a similar character, its intermediate host, in addition to pigs and wild boars, can also be humans, then finches develop in its muscles.
Development broad tapeworm is accompanied by a change of two intermediate hosts: the first is a crustacean (Cyclops), the second is a fish that has eaten the crustacean. The definitive host may be a person or a predator that eats the infected fish.
Do planarians have a larval stage?
Direct developmental sexual reproduction is a type of sexual reproduction in which there is no larval stage of embryonic development. When a larval stage exists, it is called indirect development. In sexual reproduction of planarians there is no larval stage.
What classes are commas separated into? How can these classes be described and what are some representative species within each. Platyhelminths are divided into three classes: turbellaria, trematodes and cestodes. Flukes are parasites that live inside the host. Slystosome, which causes schistosomiasis, is an example of one of these. They do not have a digestive tract, and their cells are nourished by absorbing nutrients from their host.
New concepts and terms: mesoderm, skin-muscle sac, tegument, hypodermis, reduction, protonephridia (flame cells), orthogon, strobila, ganglion, gonads, hermaphrodite, direct and indirect development, final and intermediate host, miracidium, cercaria, finna, segment, armed and unarmed tapeworm.
Literature:
What are the main human diseases caused by platyhelminths?
Their best known representative species are the beef and pork tania, which are human parasites. Main features of tilemints. How can Platyhelminths be described according to examples of representative species, basic morphology, type of symmetry, germ layers and coelom, digestive system, respiratory system, circulatory system, excretory system, nervous system and types of reproduction. Examples of typical species: planaria, schistosomes, tania. Germ layers and coelom: triplablar, acoelomata.
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Type Flatworms- these are animals with a body flattened in the dorso-ventral direction. They have bilateral symmetry. Unlike coelenterates, flatworms have another layer of cells between the endoderm and ectoderm - mesoderm. Hence another name for flatworms - three-layer without a body cavity. In flatworms it is filled parenchyma(loose cellular substance where internal organs are located).
Type Flatworms divisible by seven classes:
- Monogenea(Monogenea). Previously, this class was called monogenetic flukes.
- Cestodeformes(Cestodaria).
- Tapeworms(Cestoda).
- Trematodes(Trematoda).
- Gyrocotylides(Gyrocotyloidea).
- Aspidogastra(Aspidogastrea).
- Eyelash worms(Turbellaria) is a paraphyletic group of organisms that has class rank only formally.
Reproductive system of flatworms is hermaphroditic and very complex. In addition to the testes and ovaries, it includes various formations that serve to carry out fertilization, create protective membranes around the embryo and provide the egg with nutrients.
Flatworms most often develop through many metamorphoses. Before reaching the sexually mature stage, flatworms usually go through a series of larval stages. Without complex transformations, flatworms develop in extremely rare cases.
